Antifouling paints are used in general to prevent and delay the fouling of underwater structures (e.g. ships' bottom, docks, fishnets, and buoys) caused by various marine organisms such as shells, seaweed and aquatic bacteria. When such aquatic organisms adhere and propagate on an underwater structure like the bottom of a ship, the surface roughness of the whole ship may be increased to induce decrease of velocity of the ship and subsequently increase of fuel consumption. The removal of these aquatic organisms from the ship's bottom requires much labour and a long period of working time. In addition, if these aquatic organisms adhere and propagate on an underwater structure such as a steel structure they deteriorate their anticorrosive coating films leading to a reduction of the lifetime of the underwater structure.
Underwater structures are therefore preferably coated with an antifouling paint employing polymers containing various hydrolysable groups and more specifically organosilyl groups. Several antifouling paints are known.
EP 0 297 505 for example relates to an antifouling paint that contains a polymer having organosilyl groups and/or organopolysiloxane groups in side chains. Since the organopolysiloxane group is derived from dehydrating condensation or like means of silicon oil with methacrylic acid, this document refers to a mixture of oligomers having different numbers of the recurrence of the organosiloxane group.
WO 84/02915 and JP 63215780 describe an antifouling paint of the hydrolysable self-polishing type employing a methacrylic ester polymer having triorganosilyl group in side chains or a similar polymer. Other examples related to the use of organosilyl acrylate polymers in antifouling compositions are EP 1 127 902, EP 1 127 925, JP 63118381, WO 96/38508, EP 0 802 243, EP 0 714 957, JP 07018216, JP 01132668, JP 01146969 and U.S. Pat. No. 4,957,989 hereby incorporated by reference.
The polymers used in the above-described antifouling paints are based on silylated carboxylate monomers.
Several processes are known as conventional techniques for the synthesis of said silylated carboxylate monomers.
JP 5306290 for example describes a process to obtain a methacrylic functional group-containing organosilicon compound. The process comprises reacting methacrylic acid with a halogenoalkylsilane e.g. trialkylsilylchloride in the presence of a tertiary amine compound having a cyclic structure. This process has disadvantages such as the reduced availability and storage stability of the silyl chloride. Moreover, the reaction yields as a by-product a hydrogen halide, which provokes the corrosion of the production equipment, or a halide salt, which has to be removed by filtration.
The synthesis of trimethylsilyl methacrylate from methacrylic acid and trimethylsilyl chloride is disclosed in Fedotov. et. al. Zh.Prikl.Khim. (1971), 44(3), 695. The synthesis of trimethylsilyl methacrylate from methacrylic acid and hexamethyldisilazane is described in A. Chapman & A. D. Jenkins J. Polym. Sci. Polym. Chem. Edn. vol 15, p. 3075 (1977). This method has the disadvantage of producing ammonia.
JP 10195084 discloses the reaction of unsaturated carboxylic acid such as acrylic acid or methacrylic acid with a trialkylsilylhydride compound in the presence of a copper catalyst. One of the disadvantages of this method is the risk of hydrogenation of the unsaturated carboxylic acid due to a side reaction of the produced H2 on the is carbon-carbon double bond.
U.S. Pat. No. 6,063,887 describes 1-acyloxyorganotetrasiloxane obtained by the reaction of hexamethylcylcotrisoloxane with an acyloxysilane.
An object of the present invention is to provide a novel process capable of readily preparing polyorganosilylated carboxylate monomers or polymers thereof in a high yield from easily available starting materials.
Another object of the present invention is to provide a more direct method for the synthesis of such polyorganosilylated carboxylate monomers or polymers thereof, with easy work-up procedures.
A further object of the present invention is to provide a novel process offering an improvement vis-à-vis of the disadvantages disclosed above.